Field of the Invention
The present invention relates to sliders for use with magnetic data recording and retrieval systems and more particularly to air bearings for use on such sliders.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatus such as computers. In FIGS. 1A and 1B, a magnetic disk data storage system 10 of the art is illustrated which includes a sealed enclosure 12 and a plurality of magnetic disks 14 each of which has an upper surface 16 and a lower surface 18. The disks are supported for rotation by a spindle 20 of a motor 22.
An actuator 24 includes an E-block 25 having at its distal end a plurality of actuator arms 26. The actuator also includes a bearing 27 which mounts the actuator 24 pivotally within the enclosure 12 and further includes a voice coil 28 at its proximal end. The voice coil is disposed between a pair of magnets 30 which are fixedly connected with respect to the enclosure 12. Generating an electrical current in the coil 28 induces a magnetic field about the coil. Interaction between the magnetic fields of the coil 28 and the magnets 30 provides a desired, controlled pivotal movement of the actuator about a pivot point 31 of the bearing 27.
The actuator arms 26 support a plurality of suspensions 32, each of which supports at its distal end a slider 34a, 34b. Each suspension holds its corresponding slider in close proximity to a surface of one of the disks 14 to facilitate reading and recording data to and from the disk 14.
The motor 22 and spindle 20 cause the disks 14 to rotate. As the disks 14 rotate, the air immediately adjacent the disks moves with the disks as a result of friction and the viscosity of the air. Thus moving air passes between each of the sliders 34b, 34a and its adjacent disk surface 16, 18 forming an air bearing. This air bearing causes the head to fly a very small distance from the disk surface 16, 18.
With reference to FIG. 1C, the slider is generally in the form of a ceramic block having a leading edge 36 a trailing edge 38, first and second lateral sides 40, 42 opposite one another, and an air bearing surface generally referred to as 44. The air bearing surface includes first and second laterally opposed rails 46, 48. Each rail 46, 48 has an inward turning foot portion 50, 52 at its end closest to the leading edge 36 of the slider 34. The foot portions 50, 52 define therebetween a channel 54. A pad 56 is formed on the air bearing surface 44, located at the trailing edge 38 of the slider 34 centrally between the lateral sides 40, 42.
The raised surface areas of the rails 46, 48 and pad 56 generate a high pressure area thereunder causing the slider 34 to fly above the disk 14 passing thereunder. The location of highest pressure is located at the forward portion of the pad 56. A cavity 58 defined by the inner edges of the rails 46, 48 aft of the channel 54 generates a relatively low pressure area which provides stability during flight of the slider 34. As will be appreciated with reference to FIG. 1C, the air bearing surface 44 and associated rails 46, 48 and pad 56 are symmetrical about a longitudinal axis, centrally located between the sides 40, 42. As the slider 34 flies, any roll experienced will be about this centrally located longitudinal axis. As will be appreciated, any such roll will have relatively little effect on the fly height at the central location of the pad 56.
With reference to FIGS. 1D and 1E, each of the sliders 34 has within it a read element 60 and a write element 62. As the disk surface 16 or 18 moves past the slider 34 the write element 62 generates a magnetic field leaving magnetic data on the passing disk 14. Such write elements are generally in the form of an electrical coil 64 passing through a magnetic yoke 66. As a current passes through the coil 64 it induces a magnetic field which in turn generates a magnetic flux in the yoke 66. A gap 68 in the yoke causes the magnetic flux in the yoke to generate a magnetic field which fringes out from the gap 68. Since the gap is purposely located adjacent the disk, this magnetic fringing field imparts magnetic data onto the passing magnetic disk 14. The coil 64 is embedded within a dielectric material 70 which electrically isolates it from the yoke 66. An insulating layer 72 covers the entire write element 60.
With continued reference to FIGS. 1D and 1E, to read data from a disk 14 the read element 60 detects changes in surrounding magnetic fields caused by the disk 14 passing thereby. Several read elements may be used to read such data. A very effective read element currently in use is a GMR Spin Valve sensor 74. Such sensors take advantage of the changing electrical resistance exhibited by some materials when a passing magnetic field affects the magnetic orientation of adjacent magnetic layers. At its most basic level, a GMR spin valve includes a free magnetic layer and a pinned magnetic layer separated by a non-magnetic layer such as copper. The pinned layer has magnetization which is pinned in a pre-selected direction. On the other hand, the free layer has a direction of magnetization which is perpendicular with the pinned layer, but is free to move under the influence of an external magnetic field such as that imparted by a passing magnetic recording medium. As the angle between the magnetic directions of the free and pinned layers changes, the electrical resistance through the sensor changes as well. By sensing this change in electrical resistance, the magnetic signal passing by the read element can be detected. The sensor 74 is embedded within a dielectric layer 76, between a shield 78 and the yoke 66 of the write element 62.
With reference now to FIG. 1F, in order to take advantage of a greater amount of available disk surface area for data recording, manufacturers have used a side rail slider 80. Similar to the earlier described slider 34, the side rail slider 80 has a leading edge 82, a trailing edge 84 and first and second lateral sides 86, 88. The side rail slider also has first and second rails 90, 92. The side rail slider 80 differs from the previously described slider 34 in that the side rail slider 80 has a pair of pads 94, 96 which are located at opposite lateral sides 86, 88 of the slider 34 along its trailing edge 84. The read and write elements 60, 62 are located in one of the pads along a lateral side of the slider 34. This is advantageous in that it allows data to be recorded and read right up to the outer edge of the disk which would not be possible if the read and write elements 60, 62 were located centrally on the slider.
However, since the slider has a generally uniform configuration, the roll axis of the slider runs longitudinally along the center of the slider 34. This means that as the slider 34 rolls during flight, the fly height of the slider at the read and write elements 60, 62 will change, resulting in degraded performance. Therefore there remains a need for an air bearing design for a slider which will allow data to be read right up to the edge of the disk while maintaining a relatively constant fly height at the locations of the read and write element.